Fetal renal Doppler and urine production rate: Non‐invasive predictors of fetal inflammatory response syndrome in preterm prelabor rupture of membranes—An observational study

OBJECTIVE: To assess the role of fetal renal artery Doppler indices, specifically the pulsatility index (PI) and resistive index (RI), along with reduced fetal urine production rate (FUPR) in predicting fetal inflammatory response syndrome (FIRS) in women with preterm prelabor rupture of membranes (PPROM). METHODS: A prospective, observational study was conducted in a tertiary care center of 160 singleton pregnancies between 28 and 36 weeks of gestation with PPROM. Fetal renal artery Doppler measurements (PI and RI) and FUPR estimation by measurement of bladder volume were performed weekly using ultrasound until delivery. At delivery, cord blood was collected for IL-6 quantification, and placental tissue was examined for histologic evidence of FIRS. FIRS was defined as IL-6 levels ≥11 pg/mL and/or histopathologic findings of funisitis/chorionic vasculitis. Statistical analyses including receiver operating characteristic (ROC) curves were performed, with P < 0.05 considered statistically significant. RESULTS: Of the 160 participants, 103 (64.4%) were diagnosed with FIRS. The mean IL-6 concentration was significantly higher in the FIRS group (210.40 ± 133.70 pg/mL vs. 7.44 ± 2.01 pg/mL, P < 0.001). Fetal renal Doppler indices were significantly elevated in the FIRS group (PI: 2.93 ± 0.08 vs. 2.41 ± 0.11, P < 0.001; RI: 0.96 ± 0.04 vs. 0.88 ± 0.03, P < 0.00). Reduced FUPR (<5th percentile for gestational age) was observed in 99% of FIRS cases. FUPR had significant inverse relationship with fetal renal Doppler indices. ROC analysis identified a PI ≥2.8 as the optimal cutoff for predicting FIRS, with 98.8% sensitivity and 100% specificity. CONCLUSION: Fetal renal artery Doppler indices offer a reliable, noninvasive method for early prediction of fetal inflammation, enabling timely interventions to improve maternal and neonatal outcomes.